Technical Report 480

TARGET INFORMATION PROCESSING:

THE EFFECTS ON REACTION TIME OF

TERRAIN, DOWNLOOK ANGLE, AND

RESPONSE PROCESSING LEVEL

Rici .rd M. Johnson

U. S. Army

Research Institute for the Behavioral and Social Sciences

SOctober 1980

Acoroved fo- Public release; distribution unlimitej.

;6 Ai 0 0o4

mom1
U. S. ARMY RESEARCH INSTITUTE

FOR THE BEHAVIORAL AND SOCIAL SCIENCES

A Field Operating Agency under the Jurisdiction of the

Deputy Chief of Staff for Personnel

F•ANKLIN A. HART

JOSEPH ZEIDNER Colonel, US Army

Technical Director Co-mmander

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DISTRIBUTION Primary distioution of tts report hes boon made by ARI, Please address corresoonaeniii

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OTE ise I.noings in this repor are not to be Ct'nstrueld as an official Department o# the Army position

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Unclassified SECURITY CLASSIFICATION OF THIS PAGE (1rhe. Daoe Enteiel

"REPORT DOCUMENTATION PAGE B.FORZ COMPLFT0°G FORM

rq 0 ;*a- ' ' . GOtvT ACCEMION wo 1. RCIPIENT'S CATALGO NUMBER

gechnical eA• 480U N A _ b qI

4. TITLE (4.Ad3bll*7.7 S. TYPEC OF REPORT 6 PIRJOr CeVERED

kARGET ,NFORMATION ROCESSiNG: PHE EFFZ" .;,I

ACTION TIME OF IN, DOWNL&K 9GLE. -R T SPONSE .CESSG LEVELRMNG O. REPOMT NUER

7. AUTHOR(a) OK GRA'T Nt'rNERfe)

.

4 .ichard M.Johnson

S. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT. PROJECT. TASK

U.S. Army Research Institute for the Behavioral ._--REAS WORq UNIT NUMeERS

and Social Sciences /l ll B

5001 Eisenhower Avenue, Alexandria, VA 22333 -2QI611FIA91B,,/

11. CONTROLLIN3 OFFICE NAME AND ADDRESS 12. R9PORT DAT_

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Unclassified

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Approved for public releatse; diistribution unlimited.

17. DISTRISUTION STATEMENT (of the abestrat materei Bl ick "9, It ifflermt bu Repot)

IS. SUPPLEMENTARY NOTES

IP. KEY WOROS (Cont•nue on reveree olda It noeeaem' mad Idemtlfy by block number)

Target identification Reaction time

Target recognition Visual performance

Target acquisition

Information processing

2& A"T"ACr rhia. - mew.e N mmusy a" Ndokl# bybak bok )

/ This experiment explored the applicability of a serial exhaustive memory

scan as a model of the observer's cognitive behavior in a target acquisition

task. Reaction times were examined for identification, recognition (friendenemy), and set responses to stimulus scenes consisting of armored veiicles

varying in background (forest road, or plain) and downlook angle (10O, 200,

or 300). Positive set size was eith3r one, two, or four vehicles. The results provided support for the serial exhaustive model in the linear set size

4 .. (Continued,

DD~~ 43 ~~~ EIiWDIUV5 ~Unclassified4 ~ ~ J/ 2Lt6

±SCJRITY CLAMPCAY1@W 1op mIS AIE Data ered)
17n,- 1 A •czi f i ,OA

SECURITY CLASSIFICATION OF THIS PAGECWhen Dola e aEi.)

Item 20 (Continued)

fwuction with a zero intercept of 1.4 seconds (s) and a slope of .2 s. Parallel

functions were obtained for the forest condition adding .2 s over the equivalent

road and plain conditions. The 100 downlook angle resulted in the slowest

response times, and the 2 0 q, angle the fastest. The response times were the

fastest for the positive se•,items only, followed in order by recognition and

identification responses.

6

ii Unclassified

SECURITY CLASSIFICATION OF THIS PAGE(WTen Date Enterec
Technical Report 480

TARGET INFORMATION PROCESSING:

THE EFFECTS ON REACTION TIME OF

TERRAIN, DOWNLOOK ANGLE, AND

RESPONSE PROCESSING LEVEL .

RichardM. Johnson jvA: I

Dist ..

Submitted by:

Pabert M. Sasmor

Director, Basic Research

Approved by:

Joseph Z•idner

Technical Director

U.S. ARMY RESEARCH INSTITUTE FOR THE BEHAVIORAL AND SOCIAL SCIENCES

5001 Eisenhower Avenue. Alexandria. Virginia 22333

Office, D)eputy Chief of S'aff for Personnel

'Oepartment of toe Army

October 1980

Army tlmit•j:t Nim id,: BFasic Rhsewch in Target Identification

2()11 h1101A91lt

Approvcd for public realse: djistrbuttion unlimited.

.i
ARI Research Reports and Technical Reports are intended for sponsors of

R&D tasks and for other research and military agencies. Any findings ready

for implementation at the time of publication are presented in the last part

of the Brief. Upon completion of a major phase of the task, formal recommendatiGns for official action normally are conveyed to Fippropriate military

agencies by briefing or Disposition Form.

iv
FOREWORD

The U.S. Army Research Institute for the Behavioral and Social Sciences

(ARi) conducts research concerned with understanding and improving personnel

performance and training This report presents results of an In-House Laboratory Independent Research (ILIR) project on the development of an information processing model of target acquisition funied under Army Project

2Q161101A91B. Previous research has been concei-ned with application of

principles of learning and perception to training programs in target identification (ARI Technical Report 79-A13, Research Report 1216, and Technical

Paper 358). This report explores the perceptual and cognitive processes of

the observer in target recognition and identification.

0I P R

rc ~nical ictor

- - - - -.... ..-
TARGET INFORMATION PROCESSING: THE EFFECTS ON REACTION TIME OF

TERRAIN, DOWNLOOK ANGLE, AND RESPONSE PROCESSING LEVEL

BRIEF

Requirement:

Successful target acquisition on the battlefield requires that detection, recognition, and identification of the target followed by deployment

of the appropriate weapon system be accomplished in less than 30 seconds (s).

The target acquisition task takes on great importance as complexity increases

as a function of the number of different types of armored vehicles, aircraft,

and other potential threat targets. In addition, nations may have weapons in

their inventories from both friendly and traditionally hostile countries.

Thus, distinguishing friend from enemy becomes a complex task.

The objective of the present research was to determine reaction times

required to make recognition (friend-enemy) and identification responses to

armored vehicles under various viewing conditions. The data from this effort will provide input to the development of a model of the human observer

in the target acquisition process.

Procedure:

Scale models (1:87) of armored vehicles were viewed by enlisted personnel as background (forest, road, or plain) and downlook angle (100, 200, or

300) was varied. The observers were asked either to identify, recognize

(friend-enemy), or determine only if the vehicle was a member of the positive set, as designated in instructions. The positive set of relevant targets could nunber either 1, 2, or 4. The observer's task was to make the

appropriate response as rapidly as possible after a test scene with tarqet

was exposed.

Findings:

The major results indicate that it takes approximately 1.5 s to identify

one target, with about .2 s added for each additional target that would be

possible in a given situation. When e target was against a background of

trees, another .2 s was added to response time as compared to the equivalent

plain and open road scenes. For downlook angle, the 100 angle resulted in

the slowest response times, while the 200 angle produced the fastest times.

As expected, the response time for only positive set items was the fastest

at a mean time of 1.53 s, followed by the recognition responses at 1.64 s

and identification at 2.06 s.

vii

k A
I

Utilization of Findings:

In addition to providing information concerning the effects of the spe'.

cific vaciables investigated in the present experiment, the results dnmonstrate that the choice reaction time paradigm is a useful method for study

of the target acquisition p -ýess. These data and data from subsequent experiments will provide information on the basic processes underlying the

human observer's cognitive processes during target acquisition. By understanding the process of target acquisition and the ways various parameters

systematically affect it, meaningful input can bu made to programs on target identification, camouflage techniques, and vehicle design.

viii
TARGET INFORMATION PROCESSING: THE EFFECTS ON PEZ\iCTION TIME OF

TERRAIN, DOWNLOOK ANGLE, AND RESPONSE PROCESSING LEVEL

CONTENTS _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Page

INTRODUCTION.......................................................................1

METHOD..............................................................................2

Observers.......................................................................2

Stimuli and Apparatus...................................................4

Design...................................................................4

Procedure................................................................5

RESULTS.............................................................................6

DISCUSSION.................................................................11

CONCLUSIONS................................................................1.4

REFERENCES.........................................................................15

DISTRIBUTION......................................................................17

LIST OF TABLES

Table 1. Research design........................................................5

2. Confusion matrix for vehicle identification .................... 12

LIST OF FIGURES

Ficgure 1. Ideal serial exhaustive model...................................3

2. Mean reaction time as a function of positive set size . . . . 7

3. Mean reaction time for positive set size by background. . 8

4. Mean reaction time for positive set size by downlook angle . 9

5. Menreaction time for positive set size by response level 10

ix

- .- -- - - *----- ~ '--- -
TARGET INFORMATION PROCESSING: THE EFFECTS ON REACTION TIME OF

TERRAIN, DOWNLOOK ANGLE, AND RESPONSE PROCESSING LEVEL

INTRODUCTION

On the modern battlefield; with its highly accurate lethal and rapidly

deployable weaponry, it is critical that the soldier be able to detect,

recognize, identify, and acquire targets rapidly. This skill is essential

to insure survival of U.S. forces as well as to engage the enemy effectively.

First, detection must be mt~--determination -hat a potential target exists.

Recognition, used here to mean the friend-enemy determination, is complicated by the presence of equipment from traditional threat nations in the

arsenals of potential U.S. allies. Thus, the soldier will have to cope

with a large variety of equipment, some of which may be either friend or

3nemy. Second, once the friend-enemy determination is made, identification

of the specific vehicle or aircraft type may be important from an intelligence viewpoint and for determination of weapon vulnerability. Finally, the

target must be acquired and destroyed with the appropriate weapon system.

All of this must be done in less tban 30 s end at ranges often exceeding

3,900 m. Detection alone can be extremely difficult at this range.

A voluminous 'iterature on the target acquisition process has been revie'ed by Jones, Freitag, and Collyer (1974). Examining this review makes

i, -.vident that more attention has been given to physical and geometric

properties of scenes, sensing and display systems, and capabilities of the

hu.nan visual system than has been given to the cognitive processes of the

observer. Certainly these noncognitive aspects of tqe problem are important,

.ýut regardless of the clarity of the image that can be presented1 to the observer, the observer must still extract the relevant information. It is important to determine the effects of physical variables (e.g., camouflage,

clutter, contrast) and response variables (e.g., recognition versus identification) on human processing times in the target acquisition process.

If one examines what the observer must do in the target acquisition

process once detection has been made, one sees that the problem is one of

choice or decisionmaking at the recognition and identification level. The

observer has a set of possible choices ranging from friend-enemy in recognition to many potential choizes in identification. For example, at least

25 NATO-Warsaw Pact armored combat vehicles could be in the identification

set. For a given situation, it is hoped the set would be smaller. Of

course, the choice must be made in the shortest possible time. This process

lends itself to study as a choice reaction time situation. The choice reaction time paradigm has been used to study information processing, starting

at least with Donders' work in 1868-69 (Donders, 1969). Donders felt that

the duration of mental processes could be revealed by the appropriate arrangement of experimental tasks. Since Donders, a large volume of research

has used the choice reaction time paradigm, especially in the pasc 20 years

with the su'rge of interest in the study of cognitive pirocesses or human information processing. For recent reviews of this I Lerature see Smith (1968),

Pachella (1974), and Teichner and Krebs (1974).
One modern view of choice infomnation processing that appears particularly relevant to the target acquisition ?roblem views the process as a

serial exhaustive memory scan (Sternberg, 1969, 1975). In a typica) experimental situation, the digits 0 through 9 represent a total memory set.

A subset of these digits is given to the observer and is designated as the

positive set. The remaining digits constitute the negative set. A digit

is presented visually and the observer responds as rapidly as possible as

to whether the digit is a memt.r of tne positive or negative set. According to the serial exhaustive model, a memory scan of lhp powitivp qet igq

made in a serial fashion, with each comparison resulting in either a match

or mismatch. Each comparison takes a finite and constant amount of time.

Thus, as illustrated by hypothetical data in Figure 1, reaction time increases in a linear fashion as a function of positive set size. The slope

of the function gives the time needed for one comparison, which was arouid

38 milliseconds (msec) in Sternberg's ex4periments using digits. The posi--

tive and negative response functions have equal slopes. This indicates thait

the process is exhaustive. Otherwise, the positive response function would

have half the slope of the negative function in the case of a self-terminating

search, which stops when a match is obtained (Sternberg, 1975). The Y intercept in Sternberg's work usually was around 400 msec and represented processing other than memory scanning. One component of this processing can be conceptualized as an image "cleanup" or preprocessing stage. If the stimulus

was degraded by superimposition of a checkerboard pattern, the slope of the

function remained the saxiie (see Figure 1) but the Y intercept increased in

comparison to the nondegraded conditions (Sternberg, 1967). Thus, once the

stimulus is cleaned up, the comparison scan occurs as u"lial.

In the present experiment, armored tanks were used as stimuli in an

experimental paradigm similar to Sternberg's to determine if the observer

in a target acquisition setting behaves in a manner similar to observers in

a choice situation with digits or letters. The variables examined were number of different tanks (positive set size), terrain as a *'otential degrading

variable, viewing angle of the observer with respect to the target, and type

of response required (positive versus neqati-e set, recognition, or identification). These data will provide an initial data base and framework for

the development of a model of the observer in the target a,.quisition process. 1

METHOD

Observers

The observers were 15 enlisted military personnel from the Military

District of Washington. Both males and females in a variety of Military

Occupational Specialties were represented in the sample.

1

I would like to thank Ms. Susan Burbidge and Ms. Lucy Baker for their assistance in collecting and analyzing the data from thij experiment.

2
C4DEGRADED

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1 2 4

POSITIVE SET SIZE

Figure 1. Ideal serial exhaustive model.

3

!.7
Stimuli and Apparatus

Eight armored vehicles were photographed on either a .:87 scale terrain model or on a white homogeneous background. Four vehizles were of

U.S. origia (M60Al, M60, M48, and M103,, and four were Soviet vehicles

(T62, T55, T10, and PT76). Each vehicle was photographed in side profile

against a background of trees, on an open road, or against a homogeneous

white background. At each background position, downlook angle was varied

to produce stimuli at 10-, 20-, and 30-deg angles. Photographs from a fourth

angle of zeio deg were taken with the homogeneous background to be used as

training stimuli. The 35mm black-and-white photographs were presented in

2-inch x 2-inch slide format. The observer was situated 145 cm from a

POLACOAT2 screen on which the stimulus slides were rear-projected by two

Kodak RA960 random access projectors. At this distance the target vehicles

subtended approximately 2 deg of visual angle and simulated an actual viewing distance of about 200 m, or about 2,600 m if viewed through the 13x

optics of a tube-launched, optically tracked, wire-command linked guided

missile system (TOW) sight. The total field of view was 40 x 60 deg. An

Automated Data Systems 1800E minicomputer controlled the projectors, each

fitted with solenoid-actuated shutters. One projector presented a fixation

point that coincided with the target position on each of the stimulus

presentations.

Design

Using reaction time as a dependent variable, five independent variables

were examined in the present experiment. A summary of the design is presented in Table 1. In a factorial design the target background could be

either forest, a road through open terrain, or a plain homogeneous backdrop.

These will be referred to as forest, road, and plain conditions, respectively.

The second independent variable of interest was downiook angle, which could

be 10, 20, or 30 deg. The third variable was the size of the positive memory

set designating the targets to be responded to during a given trial block.

This variable was designated set size and could take on values of 1, 2, or

4 targets. The fourth variable was response times to positive set versus

negative set items. This was a procedurally defined variable rather than

one manipulated experimentally. The probability of either a positive or

negative set target was always .5. The fifth independent variable, Response

Level, was the only between-subjects variable. One group of five observers

responded only as to whetl-ir the target was in the positive or negative set

(set response). A second g;:oup of fi' e observers was asked to make a friendenemy determination (recognition), and the third group was asked to specify

the model number of the vehicle (identification).

2

Product names are used only 41r precision of description and do not reflect

endorsement by the Department uf the Army.

4
Table 1

Experimental Design for Each Independent Variable: Positive

Set Size, Downlook Angle, and Background

Response Set size 1 i

level 10 deg 20 deg ...... 30 deg _

group Forest Road Plain Forest , Road Plain Forest Road Plain

Set response

Recognition __

Identification

Note. Only set size 1 is illustrated. The enti~e table would be repeated

for set sizes 2 and 4 for each variable.

Procedure

Before beginning the experiment, it was necessary to train the observers

to identify the eight armored vehicles. During the training session each

observer viewed profile views of each of the eight vehicles photographed on

plain backgrounds (i.e., zero degree, plain background). The observer initiated a tzaining trial by pressing a button to expose a slide. When the

observer identified the vehicle, the button was again pushed. This removed

the slide, leaving a blank screen while the observer made identification

by selecting one of eight buttons labeled with the model number of each tank.

Once the response was made, a feedback slide provided the correct idenLification. Each vehicle was presented in random order every eight trials. During the first eight training trials the experimenter identified each vehicle

for the observer as the use of the observer's response panel was explained.

The experimenter pointed out distinctive features of each vehicle and answered

any questions. After the first eight trials, the observer was left to work

alone until three consecutive vlocks of eight errorless trials were obtained.

If this criterion was not achieved in 30 minutes, the experimental trials

were nitiated.

Followiing the training session, each observer viewed nine blocks of 72

experimental tridls each in which background, downlook angle, and vehicle

model were factorially combined. The observers were assigned to the three

response levels on the basis of order of arrival for the experiment. Each

: observer received three blocks of trials at set size 1, 2, and 4. The order of trial blocks was counterbalanced among observers. Prior to the beginning

of each trial block, the appropriate positive response set was given to the

observer, and the observer viewed each vehicle once as a refresher. Three

blocks of 72 trials were then given with that positive response set. The

first biock was considered a practice block, and the data analysis was performed on only blocks 2 and 3 for each set size.

i 5 .... A.
Before each trial began, a fixation field was presented with a small

dot indicating the position of the target in the next stimulus scene. The

observer was instructed to fixate the point and then initiate a trial by

pushing a button labeled "signal." This action resulted in the presentation

of the stimulus. As soon as the observer made a decision consistent with

the -esponse group instruction (e.g., recognition). the signal button was

again pushed, causing the stimulus to be replaced by the next fixation field.

At this time the observer entered the appropriate response information by

depressing another button. The recorded reaction time (RT) was the time between the first and second activations of the signal button. The observer

could then initiate another trial at his oi her own pace. The observers

were asked to respond as rapidly and accurately as possible. At the end of

the nine trial blocks, the observer was completely debriefed and any questions answered.

RESULTS

The major analysis consisted of a 3 x 3 x 3 x 3 x 2 analysis of variance (ANOVA) with the first factor (response level) a between-sIbjects variable and all other within-subjects factors--background, angle, set size, and

response type, respectively. Each observer made six responses for each

level of the within-subjects variables over two trial blocks. Thus, Che RT

scores in msec entered into the ANOVA were based on 12 responses for each

observer. Only correct responses were included in this aralysis.

The main effect of set size, shown in Figure 2, was reliable, F(2,24) =

3.24, R < .05. The function is essentially linear with a significant linear

trend, F(l, 24) = 11.70, p < .01, and no significant nonlinear components.

The slope of this function is approximately .2 sec with a Y intercept of

about 1.4 sec. The main effect for response type (i.e., negative versus

positive responses) was not significant. Thus, the data on the set size

effect are consistent with a serial exhaustive memory search model.

A .tati.stically signif, ant baukyround effect was obtained, F(2,24)

5.72, k < .01. The set size function for each background condition is shown

in Figure 3. The interaction was not significant. It can be seen that Rrs

for the road and plain background conditions did not differ. This observa--

tion was substantiated by multiple comparison using Duncan's New Multiple

Range Test (P < .05). Thus, the main effect of background is accounted for

by the forest condition.

action was not significant. The main effect of angle was significant,

F(2,24) = 3.69, p < .05. The 10-degree stimuli had the slowest RTs, followed

by the 30-degree and 20-degree stimuli in order. In the main effect, these

three stimuli were all significantly different from each other (Duncan,

< .05). However, in the interaction plotted in Figure 4, this effect was

evident only for set size 4. The set of points for set size 1 and 2 did not

differ b- Duncan's test.

Figure 5 presents response lervel for each set siz,2. There was no significant main effect of, or interaction with, this varLable. This was a betweensubjects variable, and there was considerable between-subjects variability

6
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POSITIVE SET SIZE

Figure 2. Mean reaction time as a function of positive set size.

7
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Figure 3. Mean reaction time for positive set size by background.

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9
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Figure 5. Mean reaction time for positive set size by response level.

10
in the present study. The wvean RT was 1.53 sec for the set response, 1.61

sec for recognition, and 2.06 sec for identification.

The error rate was much higher than is usually obtained or desired in

choice reaction time study. During training, it was clear that dislcrimi'nation of eight armored vehicles is not an easy task. Only 6 of the 15 observers reached the cr erion of three consecutive errorless trial blocks.

Two observers had three errorless trial blocks, but not consecutively. Four

observers had no errorless trial blocks. This factor could certainly increase error variance in the present analysis. However, an ANOVA of percent

errors during the experimental trials showed no differences between the thiee

response level groups. There was a significant main effect of set size, with

error rates of 15%, 20%, and 30%, respectively, for the 1, 2, and 4 set size

conditions, F(2, 24) = 4.42, £ < .01.

Table 2 shows a confusion matrix containing conditional probabilities

for each possible response to the presentation of a particular vehicle. This

table contains data from only the group of observers in the identification

condition. The breakdown was not possible for the set response or recognition groups. It is clear that the vehicles were not equally discriminable.

A chi-square test on the frequency of correct responses supported this obgervation, X2 (17) = 24.32, p < .001. The Soviet PT76 was by far the easiest

vehicle to identify, while the M103 was the most difficult; it was identified

as the M60A1 15% of the time. The T55 was identified as the M60 on 27% of

the trials. In tcrms of confusion between friendly and enemy vehicles,

enemy vehicles were identified as friendly on 11% of the trials, and friendly

vehicles were identified as enemy on slightly less than 7% of the trials.

Thus, there tends to be a bias toward making a friendly Jientification.

Table 2 shows the mean reaction time for the correct responses in parenthesis. In general, these RTs are correlated with prcpor. 'on of correct responses (Rho = .60). Two notable exceptions are the T10 -,id T55. The T10

was ranked second in proportion correct, but it had a lori RT. On the other

hand, the T55 was ranked seventh in proportion correct, but it had a short RT.

DISCUSSION

The results of the present experiment are consistent with findings

reported by Sternberg (1975) in which item recognition using letters and

digits was described by a serial exhaustive model of miemory search. As in

Sternberg's work, when RT is plotted as a function of the positive set size,

a linear function results. The slope of the function is about .2 sec, indicating that this amount of time is required to compare the target stimulus

(armored vehicle) to memory representations of the designated positive set

targets. It was also found that the rate of increa3e is the same for both

positive and negative responses. That is, when a target stimulus is presented from the negative set, the comparison process takes place at the same

rate as for positive responses resulting in parallel functions. This supports an exhaustive search model. If the search were self-terminating, i.e.,

stopping if a match is found, one would expect the positive response slope

to be half that of the negative response function. It is interesting to

compare the slopes found in the present study to those found by Sternberg.

In the typical study using letter digits, the slopes ranged from 35 to 40 msec,

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wherea-L. in the present study the slope was about 200 msec. Thus the comparison process is much slower per item with complex stimuli such as armored

vehicles.

it is also interesting to note that tht Y intercept was about 1.4 sec

in the present s..udy and averaged around 400 msec in Sternberg's work. This

time represeits processing other than the seri.al comparison during memory

scanning, Part of this time is surely represented simply in the motor componients of making the RT response. More important is the fact that the Y

intercept reflects differences in stimulus variables that degrade the stimulus. In Figure 3, the effect of the forest background is reflected in the Y

intercept but not in the scan rate, since the functions are parallel. This

situation is comparable to Sternberg's (1967) degraded stimulus condition,

in which it was hypothesized that a stimulus encoding or cleanup phase precedes the scanning stage. During this phase a clear image of the stimulus

is formed, and then the serial exhaustive scan proceeds. In the present

experiment, approximately 200 msec were needed to clean up the forest. The

cleanup completed, the scan took place at the same rate as if a plain background were present. The results of the target on a clear road were comparable to those on a plain background.

Cormparable analysi. can be made for the downlook angle results shown

in Figure 4, althoigh the results are not as clear-cut It was expected

that the 10-deg downlook angle would result in the fastest RTs since the

original training stixmuli were 0 deg. Thus, from results on mental rotaticii of visual objects (e.g., Cooper & Shepard, 19)3), one would expect

that prior to the memory scan the target would be rotated to match the most:

fimiliar angle, O-deg side as in the training stimuli, and then the scan

would proceed. The results for the 20- and 30-deg targets are consistent

with this interpretation. These two functions are parallel and suggest

that about .1 se,- is needed for this mental rotation. However, the 10-deg

tairgets required the largest RTs. Since the interaction was not significant, it could also be that the higher lookdown angles provide a better

target for identification regardless of the orientation of the training

stimuli. Some observers indicated that the higher angles were easier to

work with. These lookdown angles do provide more of the target total area

to work with.

The response level data were plagued by large between-subjects variaLilit-y and did not yield statistically xcliab1,, iult,; however, certain

i,,tce't-5.ng trends are evident. It takus about .5 sec longer to make an

idcrntification as opposed to a r-ecognit ion response, with the recognition

respor~se only .1 sec slower thdrA the positive-negative set response. From

a practical aspect, it is important to have thds information on how long

it tak-s to identify as opposed to making only a friend-enemy decision.

The information is also important from a theoretical viewpoint because it

sungests that the pr.cessing proceeds from general to specific. It was

cel:rto-inly an alternative that identifi(cAt ion of t1w vehicl(, was necessary

be•Core the friend-enemy determination could h, ntodc. Anotht-r important

a,-p~ect of this data is that the slopes (-f the t unut ions sho•wn in Figure 5

it • o ifferunt [ for e,,lch r, ,pon ,:el r; a furt'tion ,t , rnsi•i ve set size.

hius, the re:7;ponso Iw.,vel direct ly affo• ts the scannrii rat.,e and is not an

addJtive factor affecting only the Y intercept.

13

• I

•t mT'' n •- a"• P• " ' • -. _4" .. .... .. _ -. - ..... .. • . . . .. t . .. * -• " • ' "
The error rate was much higher than desired. Ideally, the serial exhaustive model assumes error-free performance, and empirical tests normally

do not show error rates greater than 5%. It is hoped this error rate will

be corrected in future work by increasing the amount of training to insure

better performance prior to beqinning experimental trials. It would also

be of inte-est to manipulate accuracy by instruction, emphasizing either speed or accuracy. This would approximate the target acquisition tasks

under more stressful conditions.

The pattern of results for each target stimulus also provides useful

information as to the discriminability of the vehicles. Inferences can be

drawn concerning the relevant cues. For example, the results suggest that

the turret shape may be the confusion point between the T55 and M60. This

is borne out by the pattern of results in that T55 was often identified as

the M60, but infrequently as the M60AI. Since the chassis on the M60 and

M60AI are nearly identical, the turret As the likely cue. In future work, 4

the M48, M103, and M60 will be replaced with more current NATO vehicles.

CONCTULIONS

The present study demonstrates that the CRT paradigm is a useful tool

for the study of the target acquisition process. It provides information

on the effects of various target acquisition parameters that can provide

input to several related programs. For example, training in tarset identification is an important activity. Many of the -udies on training effectiveness are mainly concerned with pre-post measui s of training effectiveness (e.g., Cockrell, 1979; Warnick & Kubala, 1979). Reaction time data

can provide information pertaining to emphasis to be given in training programs and to effects of different variables on the speed and accuracy of

identification responses. The area of c;amouflage and vehicle conspicuity

is another important topic of study (Warnick, Chastain, & Ton, 1979) which

is directly addressable by methods used in the present research. Finally,

the present approach provides information on the basic processes underlying

the human observer's cognitive processes during target acquisition. Understanding the observer'j cognitive processes will lead to the most fruitful

applications of the target acquisition data base.

14

k
REFER1ZNCLEi

I I E fV tc k!t t i v' tr.-13ing for tar&w ileriL i i cot iot undex dlejr~adeci

')'111t i -)ns AR I~ Technical Lwapvr 358, Apri I15)7.

rL A. & Sh,ýparl , !R. N. Chionometric ;fjci-ie!, tI t li iotat~ ion of

:Ip~rat,i M509ye5. Tii !,. G . Clios&2 (Edi.), Visual Jflciinot 105 l Oes i

Aco'lemi j- Pres,,s Lic . , 1973.

in ,(. .()n Lhe spee-d of ment~ital processes. Lii W. (-;. Kcster (Ed. Aari

in.,Attention and performance II. Amsterdam: North-Hol~and, 1.901).

'i edfrom A-c'a Psycholog ica, 1969, 30.)

1.b., I;ceitdy, M. , & (Jul lyel, S. C. Ai-t-rudtarget ac~quisi in'

;0017':2 book. A rovi -w of the lite.iatur-uz'. Orlando, Fla. :Mar t in

'l~i ric Lt-a ('i.i pyurat ori , Sept(,mbei 19ý74 . ConLract No. NOO 0 14-72-C-0389,

"nittice of Naval Research, Arlinqton, Va.

Thie hi terpretatiari ofi reactioai Lime !;, is ,"rnwtiui -j)piw(cS

re ~ i I.i ~ 11 13 . KCI i towit-z (Ed .) , Humnan Iniformiat.i~on Proessing: TutIcnroI~t

;ii P'.orr-focmiancu and Coqnitionr, Hillsdale, N.J. Lawronce "Trlbauin A ss.

E~ (Jhowec react ton time: An analysis of the major theoretical

l'OLI~~oI5.Psycholoyical Bulletin, 1968, -69(2) , 77-110.

>1 n S.nq Memory scanning: New findings and current co~ntroversies.

Journal of Expe rli mntal Psychology, 1975, 27, 1-32.

11., Krobs, M. J.. Laws, of visual cý n',c re2acio time.

~1ixaihev nj P)174, 81, 75-98.

W. . Kubata , A. :. >tlld i O'S i 11 larcpe Y inqo t ne;i~rii

W. ARTRE-ealsil L:11kccOrt 121]6, July 1979.

iF r Ch:ljatts i, G. Li, Ton, W. if. T,(pcj ranI le t..irjet rcgii

nd dýritilcat ion or camouflagel a.rmored veb i ]es. ART Technitcal R~e

P-lMily 15)79.

V)
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